中粗WC含量对Ni-Co粗晶硬质合金微观组织及性能的影响

Effect of medium coarse WC content on the microstructure and properties of Ni-Co coarse grain cemented carbide

摘要:

研究了中粗WC含量对Ni-Co粗晶硬质合金微观组织与晶粒分布的影响，进而讨论了晶粒分布对硬质合金力学性能的影响。通过金相分析了中粗WC含量对硬质合金晶粒度与邻接度的影响，并利用截线法研究了微观组织的晶粒的分布规律；研究了晶粒度与晶粒分布对磁力、密度及其它力学性能的影响。结果显示，中粗WC晶粒可均匀分布在粗晶WC周围阻碍粗晶与粘结相接触，抑制了粗晶粒的快速粗化，降低了合金平均晶粒度与平均自由程，使晶粒分布逐渐转变为双峰分布；在压力烧结下所有合金的相对密度均在99.5%以上，通过对矫顽磁力的测试分析，验证了微观组织中晶粒双峰分布的准确性；平均晶粒度的降低使合金硬度逐渐增加、断裂韧性逐渐降低；微观组织中超粗晶粒逐渐减少，有利于硬质合金抗弯强度与耐磨性的提高。在Ni-Co粗晶硬质合金中加入部分中粗WC颗粒有利于减少晶粒粗化进而提高耐磨性，加入30%中粗WC颗粒时综合性能最好。

Abstract:

The effect of medium and coarse WC content on the microstructure and grain distribution of Ni-Co coarse crystalline cemented carbide was studied, and then the effect of grain distribution on the mechanical properties of cemented carbide was discussed. The effect of medium and coarse WC content on the grain size and adjacency of the cemented carbide was analyzed by metallographic analysis, and the distribution pattern of the grains in the microstructure was investigated by using the truncation method; the effects of grain size and grain distribution on the magnetic force, density and other mechanical properties were studied. The results show that the medium and coarse WC grains can be uniformly distributed around the coarse WC grains to hinder the contact between the coarse grains and the bonding phase, which inhibits the rapid coarsening of the coarse grains, reduces the average grain size and average free range of the alloy, and gradually transforms the grain distribution into a bimodal distribution; the relative densities of all the alloys under pressure sintering are above 99.5%, and the bimodal distribution of the grains in the microstructure is verified by the analysis of the coercivity magnetism. The accuracy of the bimodal distribution of grains in the microstructure was verified by the analysis of coercivity magnetism; the decrease of average grain size gradually increased the hardness and decreased the fracture toughness of the alloy; the gradual decrease of super coarse grains in the microstructure was beneficial to the improvement of flexural strength and wear resistance of the carbide. The addition of some medium coarse WC particles to the Ni-Co coarse grain cemented carbide is beneficial to reduce the grain coarsening and thus improve the wear resistance, and the best overall performance is achieved with 30% medium coarse WC particles.